The present invention relates to an intracavity probe assembly insertable into a bodily conduit such as an endorectal or endovaginal probe. An ultrasonic transducer is carried with the probe assembly and used for obtaining an ultrasonic image of a cross section of the conduit under deformation and no deformation (relaxed) conditions.
Intrarectal and intravaginal palpation is widely used in examination of patients to detect prostate tumors and other cancers by evaluating the hardness of the palpated area of the rectum or vagina. This palpation is commonly performed using a finger of the physician and as such involves much subjectivity in determining the presence of tumors.
At the present time, intracavity probes for ultrasonic imaging are known having ultrasonic transducers capable of being inserted into bodily conduits, such as the esophagus, rectum, and vagina. These endoscopic probes are used for obtaining ultrasonic images of surrounding tissue under static conditions. The available probes provide up to 360.degree. scanning. The usefulness of such probes extends only to direct imaging and the information provided by those ultrasonic devices does not contain the evaluation of relative hardness of tissues, which can be reconstructed from the comparison of images when wall tissue is deformed at one time and relaxed at another.
Acoustic Imaging of Phoenix, Arizona sells a slightly curved endorectal ultrasonic probe with a field of scan or view that provides both transverse and sagittal scanning images of the prostate without application of forces compressing tissue.
Techniques used for intrarectal ultrasound have been discussed in literature and various approaches have been tried. See for example, Martin, J. P. Transrectal ultrasound: A New Screening Tool for Prostate Cancer", American Journal of Nursing; Page 69; February 1991. The following items in the Journal of the American Medical Association have dealt with the techniques where use of a condom on an ultrasonic probe is mentioned: Chodak, G. W.; Transrectal Ultrasonography: Is It Ready for Routine Use?; JAMA 259:18 Pages 2744-2745; May 13, 1988 and Questions and Answers: JAMA 259:18, Pages 2757-2759; May 13, 1988.
A method recently proposed for measuring and imaging tissue elasticity is described in Ophir et al., U.S. Pat. No. 5,107,837. This method includes emitting ultrasonic waves along a path into the tissue and detecting an echo sequence resulting from the ultrasonic wave pulse. The tissue is then compressed (or alternatively uncompressed from a compressed state) along the path by displacing a transducer and during such second compressing, a second pulse of ultrasonic waves is sent along the path into the tissue. The second echo sequence resulting from the second ultrasonic wave pulse is detected and then the differential displacement of selected echo segments of the first and second echo sequences are measured. A selected echo segment of the echo sequence, i.e., reflected RF signal, corresponds to a particular echo source within the tissue along the beam axis of the transducer. Time shifts in the echo segment are examined to measure compressibilities of the tissue regions. This technique is further described in Ophir et al., Elastography: A Quantitative Method for Imaging the Elasticity of Biological Tissues. Ultrasonic Imaging 13, 111 (1991).
Despite the advent of intrarectal probes for ultrasonic imaging of bodily conduit tissues, the procedure of palpating bodily conduits with a finger is still widely used. This procedure is highly subjective and does not provide complete information about the presence, location, size, and relative hardness of an inclusion (e.g. tumor). This is especially true when the tumor is small and/or far from the bodily conduit wall.